SC16 - CHEMICAL CELLS AND FUEL CELLS

Question 1

SC16a - What are the components in a chemical cell ?

Answer 1

• two different metals each dipped into a solution of one of their salts
• a salt or ion bridge to pass from one solution to another and complete the circuit

Question 2

SC16a - why might a battery go flat ?

Answer 2

One of its reactants have been completely used up so there are no more electrons flowing past

Question 3

SC16a - what two elements are used in a fuel cell ?

Answer 3

Hydrogen and oxygen

Question 4

SC16a - what is used at both sides of the fuel cell to create ions

Answer 4

Electrodes

Question 5

SC16a - explain how hydrogen atoms provide electricity to a fuel cell.

Answer 5

The hydrogen fuel enters the fuel cell. Here it reaches an electrode and becomes a hydrogen ion losing its electron. The electrons move through the circuit providing a current in the circuit. The hydrogen ion passes through the water membrane to meet back with an electron and react with oxygen atoms to form water

Question 6

SC16a - how do rechargeable batteries work ?

Answer 6

They are made out of reactants that can be reformed when electricity passes through them

Question 7

SC16a - how can potential difference be created in a fuel cell and how can its strength be altered ?

Answer 7

Metals push their electrons away with a certain force. The more reactive metal pushes its electrons to the less reactive metal which is forced to accept it, creating a potential difference. Metals with a greater difference in reactivity will create a larger potential difference. This will also create a greater current as there are more electrons passing a point over a given time

Question 8

SC16a - what are the strengths of using fuel cells / in cars

Answer 8

• produces a voltage as long as it is supplied with fuel/hydrogen and oxygen/air
• only product is water
• it does not need recharging using mains electricity (unlike battery)
• it has no moving parts (unlike petrol/diesel engine)
• quieter than petrol or diesel engine
• fits into engine bay

Question 9

SC16a - what are the weaknesses of using fuel cells ?

Answer 9

• hydrogen must be stored in the core therefore needs to liquefied or under high pressure
• there are few hydrogen stations for refuelling (unlike electrical outlets-battery)
• if hydrogen produced from coal/natural gas carbon dioxide produced- greenhouse gas
• uses platinum electrodes which are expensive
• H2 is very reactive